Casting mold, counter-pressure casting method and low-pressure casting method

ABSTRACT

The application relates to the technical field of casting and provides a casting mold, a counter-pressure casting method and a low-pressure casting method. The casting mold includes an upper mold insert arranged on an upper mold, a riser cavity is formed in a lower part of the upper mold insert, the riser cavity communicates with a mold cavity, an air pipe is arranged on the upper mold insert, one end of the air pipe is located at a top of the riser cavity, and compressed air can be introduced. The compressed air is introduced into the air pipe in the casting process, an upper part of the riser cavity forms a pressure with the same order of magnitude in a heat-insulating furnace, and the pressure of the riser is transmitted to a far-end defect position through local extrusion.

TECHNICAL FIELD

The present application relates to the technical field of casting, in particular to a casting mold, a counter-pressure casting method and a low-pressure casting method.

BACKGROUND

In the development process of modern automobiles, lightweight and energy saving are an important trend, a great difficulty is brought to the process as the casting structure is complicated, the shape is special, a larger number of iron castings are replaced by aluminum alloy, and the casting shape is complex. Casting defects are the primary process problem brought by the complex shape. At present, the main method to solve the casting defects is to optimize the product shape, so that the castings may be sequentially solidified, and the product weight will be increased, which is contrary to the development trend of the lightweight and energy saving. In addition, the casting defects may be eliminated through riser feeding, but only casting defects near the riser can be solved by using a riser, and the defects far away from the riser cannot be eliminated, which requires a new breakthrough in the process.

SUMMARY

An embodiment of the present application provides a casting mold, a counter-pressure casting method and a low-pressure casting method. The pressure of a riser is transmitted to a far-end defect position through local extrusion, thereby achieving the purpose of feeding the defect position to eliminate the defect.

To achieve the above objectives, the present application provides the following technical solution:

in a first aspect, a casting mold is provided, and includes an upper mold and a lower mold, wherein a mold cavity is formed by enclosing of the upper mold and the lower mold, an upper mold insert is arranged on the upper mold, a riser cavity is formed in a lower part of the upper mold insert, and the riser cavity communicates with the mold cavity; and an air pipe communicating with the riser cavity is arranged on the upper mold insert, one end of the air pipe is located at a top of the riser cavity, so that compressed air can be introduced.

In some embodiments, a venting plug is arranged between the riser cavity and the air pipe.

In some embodiments, a check valve is disposed on the air pipe.

In some embodiments, a cross section of the riser cavity is in a shape of cone with a narrow upper part and a wide lower part.

In a second aspect, an embodiment of the present application provides a counter-pressure casting method of the casting mold as defined in any one of the above embodiments. The counter-pressure casting method of the casting mold includes the following steps:

after the mold is closed, dry compressed air is introduced into a heat-insulating furnace and the mold cavity, pressure is increased to 0.2-0.6 MPa, then the mold cavity stops being pressurized and maintains the pressure, pressurization continues to be performed in the heat-insulating furnace at a speed of 4 mbar/s-20 mbar/s according to a set pressure curve, and the mold cavity is slowly filled with molten aluminum in the heat-insulating furnace; and

compressed air is introduced into the air pipe, the upper part of the riser cavity forms a pressure with the same order of magnitude as a mold-filling pressure in the heat-insulating furnace, and an extrusion effect is continuously formed on a riser in the solidification process of a casting.

In a third aspect, an embodiment of the present application provides a low-pressure casting method of the casting mold as defined in any one of the above embodiments. The low-pressure casting method of the casting mold includes the following steps:

after the mold is closed, pressurization is performed in the heat-insulating furnace at a speed of 4 mbar/s-30 mbar/s according to a set pressure curve, and the mold cavity is slowly filled with molten aluminum in the heat-insulating furnace; and

compressed air is introduced into the air pipe, the upper part of the riser cavity forms a pressure with the same order of magnitude as a mold-filling pressure in the heat-insulating furnace, and an extrusion effect is continuously formed on a riser in the solidification process of a casting.

Compared with the prior art, the present application has the following beneficial effects:

the present application provides the casting mold, the counter-pressure casting method and the low-pressure casting method. The casting mold includes the upper mold insert arranged on the upper mold, wherein the riser cavity is formed in the lower part of the upper mold insert, the riser cavity communicates with the mold cavity, the air pipe communicating with the riser cavity is arranged on the upper mold insert, one end of the air pipe is located at the top of the riser cavity, and compressed air can be introduced. The compressed air is introduced into the air pipe in the casting process, so that the upper part of the riser cavity forms the pressure with the same order of magnitude as the mold-filling pressure in the heat-insulating furnace, the extrusion effect is continuously formed on the riser in the solidification process of the casting, and the pressure of the riser is transmitted to the far-end defect position through local extrusion, thereby achieving the purpose of feeding the defect position to eliminate the defect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural schematic diagram of a mold closing state of a casting mold according to the present application.

In the drawings: 1—upper mold, 2—lower mold, 3—upper mold insert, 4—mold cavity, 5—riser cavity, 6—air pipe, 7—venting plug, 8—check valve, 9—flow dividing cone.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In order to solve the casting defects such as shrinkage porosity and shrinkage cavity far away from a riser, an embodiment of the present application provides a casting mold, including an upper mold and a lower mold, wherein a mold cavity is formed by enclosing of the upper mold and the lower mold, an upper mold insert is arranged on the upper mold, a riser cavity is formed in a lower part of the upper mold insert, and the riser cavity communicates with the mold cavity; and an air pipe communicating with the riser cavity is arranged on the upper mold insert, one end of the air pipe is located at a top of the riser cavity, and compressed air can be introduced. In the embodiment, compressed air is introduced into the air pipe in the casting process, so that an upper part of the riser cavity forms a pressure with the same order of magnitude as a mold-filling pressure in a heat-insulating furnace, an extrusion effect is continuously formed on a riser in the solidification process of a casting, and the pressure of the riser is transmitted to a far-end defect position through local extrusion, thereby achieving the purpose of feeding the defect position to eliminate the defect.

In some other embodiments, a venting plug is arranged between the riser cavity and the air pipe, thereby preventing molten aluminum from entering a pipeline of the air pipe during mold filling to avoid blocking the pipeline so as to avoid ineffective extrusion.

In some other embodiments, a check valve is arranged on the air pipe, so that the air pipe is further prevented from being blocked by the molten aluminum in the mold filling process, and extruded air can be ensured to successfully enter the riser cavity.

In some other embodiments, a cross section of the riser cavity is in a shape of cone with a narrow upper part and a wide lower part, and the conical riser is beneficial to formation of an ideal contracted pipe in the riser, so that the feeding efficiency of the riser is improved and a good casting is obtained.

The technical solutions of the embodiments of the present application are clearly and completely described below with reference to the accompanying drawings of the embodiments of the present application. Apparently, the described embodiments are some but not all embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts should fall within the protection scope of the present application.

Embodiment 1

The embodiment 1 provides a casting mold, as shown in FIG. 1, including an upper mold 1 and a lower mold 2, wherein a mold cavity 4 is formed by enclosing of the upper mold 1 and the lower mold 2. An upper mold insert 3 is arranged on the upper mold 1, a riser cavity 5 is formed in a lower part of the upper mold insert 3, and the riser cavity 5 communicates with the mold cavity 4. A cross section of the riser cavity 5 is in a shape of cone with a narrow upper part and a wide lower part.

An air pipe 6 communicating with the riser cavity 5 is arranged on the upper mold insert 3, one end of the air pipe 6 is located at a top of the riser cavity 5, and compressed air can be introduced. The other end of the air pipe 6 may be connected to air pressurizing equipment, for example an air pump, an air compressor or a compressed air station on a production line.

A venting plug 7 is arranged between the riser cavity 5 and the air pipe 6, thereby preventing molten aluminum from entering a pipeline of the air pipe 6 during mold filling to avoid blocking the pipeline so as to avoid ineffective extrusion.

A check valve is arranged at a position, being 200 mm away from the riser, of the air pipe, so that the extrusion pipeline of the air pipe 6 is further prevented from being blocked by the molten aluminum in the mold filling process, and extruded air can be ensured to successfully enter the riser cavity 5.

In the embodiment 1, the casting mold is provided. Compressed air is introduced into the air pipe 6 in the casting process, so that the upper part of the riser cavity 5 forms a pressure with the same order of magnitude as a mold-filling pressure in the heat-insulating furnace, an extrusion effect is continuously formed on the riser in the solidification process of a casting, and the pressure of the riser is transmitted to a far-end defect position through local extrusion, thereby achieving the purpose of feeding the defect position to eliminate the defect. After verification, the present application may produce an obvious inhibition effect on the defects within 100 mm around the riser.

The present application is simple in structure and convenient to operate, and may eliminate the casting defect that the common riser cannot be eliminated; and meanwhile, the casting is crystallized under the local pressure, the internal structure performance of the casting can be enhanced, the production quality can be improved, and a method is provided for breakthrough of the counter-pressure casting process.

Embodiment 2

The embodiment 2 provides a counter-pressure casting mold, as shown in FIG. 1, including an upper mold 1 and a lower mold 2, wherein a mold cavity 4 is formed by enclosing of the upper mold 1 and the lower mold 2. An upper mold insert 3 is arranged on the upper mold 1, a riser cavity 5 is formed in a lower part of the upper mold insert 3, and the riser cavity 5 communicates with the mold cavity 4. A cross section of the riser cavity 5 is in a shape of cone with a narrow upper part and a wide lower part.

An air pipe 6 communicating with the riser cavity 5 is arranged on the upper mold insert 3, one end of the air pipe 6 is located at a top of the riser cavity 5, and compressed air can be introduced. The other end of the air pipe 6 may be connected to air pressurizing equipment, for example an air pump, an air compressor or a compressed air station on a production line.

A venting plug 7 is arranged between the riser cavity 5 and the air pipe 6, thereby preventing molten aluminum from entering a pipeline of the air pipe 6 during mold filling to avoid blocking the pipeline so as to avoid ineffective extrusion.

A check valve is arranged at a position, being 200 mm away from the riser, of the air pipe, so that the extrusion pipeline of the air pipe 6 is further prevented from being blocked by the molten aluminum in the mold filling process, and extruded air can be ensured to successfully enter the riser cavity 5.

A counter-pressure casting method of the counter-pressure casting mold is as follows:

casting aluminum alloy (for example, ZL101 and A356 aluminum alloy) is provided; the casting aluminum alloy is molten, and molten aluminum is placed into a heat-insulating furnace of a casting machine and is poured at the temperature of 700-730° C.; after the mold of the casting machine is closed, dry compressed air is introduced into the heat-insulating furnace and the mold cavity, the pressure is increased to 0.2-0.6 MPa, then the mold cavity stops being pressurized and maintains the pressure, pressurization continues to be performed in the heat-insulating furnace at a speed of 4 mbar/s-20 mbar/s according to a set pressure curve, and slowly fill the metal casting mold cavity with the molten aluminum in the heat-insulating furnace; compressed air is introduced into the air pipe, so that the upper part of the riser cavity forms a pressure with the same order of magnitude as a mold-filling pressure in the heat-insulating furnace (to avoid danger caused by too high pressure or non-obvious extrusion effect caused by too low pressure) to form an extrusion effect on the riser in the solidification process of the casting; after mold filling is completed, each branch cooling water path in a mold core is opened to cool the mold and the pressure of the heat-insulating furnace is maintained; the pressure above the riser is relieved, and the pipeline of the air pipe is rapidly cut off from the mold cavity to ensure the cavity sealing effect in the mold cavity, and then the pressure in the mold cavity and the heat-insulating furnace is relieved; and the mold is opened, and the casting is taken out and then is rapidly soaked into water with the temperature of 30-45° C. for cooling to complete the counter-pressure casting production.

In the embodiment 2, the counter-pressure casting mold and the counter-pressure casting method are provided. Air pressure introduced above the riser is started in the casting process, compressed air is introduced into the air pipe 6, so that the upper part of the riser cavity 5 forms the pressure with the same order of magnitude as the mold-filling pressure in the heat-insulating furnace, and the extrusion effect is continuously formed on the riser in the solidification process of the casting, the pressure of the riser is transmitted to the far-end defect position through local extrusion, thereby achieving the purpose of feeding the defect position to eliminate the defect. After verification, the present application may produce an obvious inhibition effect on the defects within 100 mm around the riser.

Embodiment 3

The embodiment 3 provides a low-pressure casting mold, as shown in FIG. 1, including an upper mold 1 and a lower mold 2, wherein a mold cavity 4 is formed by enclosing of the upper mold 1 and the lower mold 2. An upper mold insert 3 is arranged on the upper mold 1, a riser cavity 5 is formed in a lower part of the upper mold insert 3, and the riser cavity 5 communicates with the mold cavity 4. A cross section of the riser cavity 5 is in a shape of cone with a narrow upper part and a wide lower part.

An air pipe 6 communicating with the riser cavity 5 is arranged on the upper mold insert 3, one end of the air pipe 6 is located at a top of the riser cavity 5, and compressed air can be introduced. The other end of the air pipe 6 may be connected to air pressurizing equipment, for example an air pump, an air compressor or a compressed air station on a production line.

A venting plug 7 is arranged between the riser cavity 5 and the air pipe 6, thereby preventing molten aluminum from entering a pipeline of the air pipe 6 during mold filling to avoid blocking the pipeline so as to avoid ineffective extrusion.

A check valve is arranged at a position, being 200 mm away from the riser, of the air pipe, so that the extrusion pipeline of the air pipe is further prevented from being blocked by the molten aluminum in the mold filling process, and extruded air can be ensured to successfully enter the riser cavity 5.

A low-pressure casting method of the low-pressure casting mold is as follows:

casting aluminum alloy (for example, ZL101 and A356 aluminum alloy) is provided; the casting aluminum alloy is molten, molten aluminum is placed into a heat-insulating furnace of a casting machine and is poured at the temperature of 680-750° C.; after the mold of the casting machine is closed, pressure in the heat-insulating furnace is increased at the speed of 4 mbar/s-30 mbar/s according to a set pressure curve (the pressurizing speed may be changed in the liquid lifting stage and the mold filling stage, for example, the speed is controlled to be 15 mbar/s-30 mbar/s in the liquid lifting stage and is controlled to be 4 mbar/s-15 mbar/s in the mold filling stage), and a metal casting mold cavity is slowly filled with the molten aluminum in the heat-insulating furnace; compressed air is introduced into the air pipe, so that an upper part of the riser cavity forms a pressure with the same order of magnitude as a mold-filling pressure in the heat-insulating furnace (to avoid danger caused by too high pressure or non-obvious extrusion effect caused by too low pressure) to form an extrusion effect on the riser in the solidification process of the casting; after mold filling is completed, each branch cooling water path in a mold core is opened to cool the mold and the pressure of the heat-insulating furnace is maintained; the pressure of the pipeline of the air pipe above the riser is relieved and then the pressure in the heat-insulating furnace is relieved; and the mold is opened, the casting is taken out, and subsequent heat treatment, machining, coating and other processes are conducted to complete low-pressure casting.

In the embodiment 3, the low-pressure casting mold and the low-pressure casting method are provided. Air pressure introduced above the riser is started in the casting process, and compressed air is introduced into the air pipe 6, so that the upper part of the riser cavity 5 forms the pressure with the same order of magnitude as the mold-filling pressure in the heat-insulating furnace, the extrusion effect is continuously formed on the riser in the solidification process of the casting, and the pressure of the riser is transmitted to a far-end defect position through local extrusion, thereby achieving the purpose of feeding the defect position to eliminate the defect. After verification, the present application may produce an obvious inhibition effect on the defects within 100 mm around the riser. 

What is claimed is:
 1. A casting mold, comprising an upper mold and a lower mold, wherein a mold cavity is formed by enclosing of the upper mold and the lower mold, an upper mold insert is arranged on the upper mold, a riser cavity is formed in a lower part of the upper mold insert, and the riser cavity communicates with the mold cavity; and an air pipe communicating with the riser cavity is arranged on the upper mold insert, one end of the air pipe is located at a top of the riser cavity, and compressed air can be introduced.
 2. The casting mold according to claim 1, wherein a venting plug is arranged between the riser cavity and the air pipe.
 3. The casting mold according to claim 1, wherein a check valve is arranged on the air pipe.
 4. The casting mold according to claim 1, wherein a cross section of the riser cavity is in a shape of cone with a narrow upper part and a wide lower part.
 5. A counter-pressure casting method of the casting mold according to claim 1, comprising the following steps: after the mold is closed, introducing dry compressed air into a heat-insulating furnace and the mold cavity, increasing pressure to 0.2-0.6 MPa, then stopping pressurizing the mold cavity and maintaining the pressure, continuing to perform pressurization in the heat-insulating furnace at a speed of 4 mbar/s-20 mbar/s according to a set pressure curve, and slowly filling the mold cavity with molten aluminum in the heat-insulating furnace; and introducing compressed air into the air pipe, forming a pressure with the same order of magnitude as a mold-filling pressure in the heat-insulating furnace on an upper part of the riser cavity, and continuously forming an extrusion effect on a riser in the solidification process of a casting.
 6. A low-pressure casting method of the casting mold according to claim 1, comprising the following steps: after the mold is closed, performing pressurization in the heat-insulating furnace at a speed of 4 mbar/s-30 mbar/s according to a set pressure curve, and slowly filling the mold cavity with molten aluminum in the heat-insulating furnace; and introducing compressed air into the air pipe, forming a pressure with the same order of magnitude as a mold-filling pressure in the heat-insulating furnace on an upper part of the riser cavity, and continuously forming an extrusion effect on a riser in the solidification process of a casting. 